1. Field of the Invention
The invention generally relates to communication systems, and more particularly to a context synchronization method performed in a mobile communication system which manages packet transmission/reception.
2. Background of the Related Art
Generally, in radio protocols of systems which perform packet-centered burst data communication such as General Packet Radio Services (GPRS), in radio protocols of a mobile communication system which have the same peer information and are not frequently updated such as a session management protocol (SM) and a mobility management protocol (MM), context synchronization of each protocol is always performed based on a client/server relationship. In general, a mobile station (MS) functions as a client while a network functions as a server. If information possessed by the client is different from that of the server when the client makes a request, the server rejects the request of the client. In such a case, a corresponding protocol layer is considered to be in an abnormal state and thus does not operate smoothly. The MS, for example, the client, should restart the synchronization procedure from the beginning.
FIGS. 1(a) and 1(b) are flowcharts of a related-art processing method of a radio protocol between a network and a MS. Referring to FIG. 1, once power of a terminal is turned on, cell selection is executed, S1. It is then judged whether a cell is selected, S2. If a cell is not selected, a search for other available cells starts, S16. If other available cells exist, the process returns to the cell selection step. If no other cells are available, service is limited and another search is performed to find other available cells, and this process is periodically repeated until an available cell is found.
If a cell is selected, the MS performs a LUP (location update procedure) or RAU (routing area update) procedure to register itself to a network, S3, and judges whether there is a problem in GMM (GPRS MM) or not, S4. If a problem exists in the GMM, the process returns to the cell selection step. If no problem exist in the GMM, a general idle and normal procedures are executed, S5. One of the following procedures are then performed: case (A)—a GMM failure occurrence in the respective MS and network, a case (B)—a PDP failure occurrence in network, and a case (C)—a PDP failure occurrence in MS. These cases are generated due to differences in CONTEXT from each other in synchronization between the network and MS.
A CONTEXT is environmental information. In other words, the CONTEXT covers information that is a part of an operating environment of an application and it can be sensed by the application. The CONTEXT typically includes the location, identity, activity and state of people, groups and objects. The application may sense its software and hardware environments to detect, for example, the capability of peripheral resources by receiving the CONTEXT
In case (B), if a PDP failure occurs in network, S6, a self-termination is executed to perform self-deactivation, S7. Then, the process waits until the terminal sends a SM or a GMM message to the network, S8. Thereafter, it judges whether the SM message is received, S9. If the SM message is not received, the process returns to the previous standby status. If the SM message is received, the SM status message confirming the reception is transferred, S10.
Then, self-deactivation of the PDP is performed, S11. Thereafter, the idle and normal procedures are performed, S12, and a user requests a PDP CONTEXT first, S13. Then, a PDP activation procedure is executed. In this procedure, first, PDP activation is requested, S14, and the PDP activation is then accepted to achieve the synchronization, S15. If the GMM becomes good again after completion of the above steps, the process returns to step S5, to perform the idle and normal procedures for normal operation.
In case (C), if PDP failure occurs in the MS, S20, a deactivation procedure to delete the previous unsynchronized CONTEXT is performed, S21. Then, the process returns to step S12, to perform the idle and normal procedures in case (B). Remaining steps S12 through S15 in case (B) are executed precisely.
In case (A), if a GMM failure occurs in the MS or in the network, S30, it is judged whether a current PDP session exists, S31. If a current PDP session exists, a self-termination procedure is performed, S32. Thereafter, the GMM is checked to determine if it is the cause, S33, and a GMM RE-ATTACH procedure is executed. On the other hand, if the PDP session does not exist in the previous S31, the RE-ATTACH procedure is directly executed.
The GMM RE-ATTACH procedure first judges whether the failure occurs in the network or MS, S34. If the failure occurs in the network, ‘paging with IMSI’ or a ‘DETACH request’ is executed, S35. Subsequently, an ATTACH procedure is performed, S36, and the process goes to the next step. If the failure occurs in the MS in S34, the ATTACH procedure is directly performed and the process goes to the next step, S37. It is then judged whether the ATTACH procedure is successfully performed or not, S38.
If the ATTACH procedure is successfully performed, the process goes to the step S12, to perform the idle and normal procedures in case (B). Similar to case (C), the steps S12 through S15 of case (B) are then executed. If the ATTACH procedure is not performed successfully, the process goes back to S1, turning on power to select the cell.
Thus, if the CONTEXTs possessed by the MS and the network are different from each other, the related-art method has the generation/modification/termination protocols only. As a result, an abnormal state may occur according to various situations of the radio network. In an abnormal state, the network and MS are unable to be informed of the information of the relative side, and therefore may fail to efficiently cope with the following operation. Hence, power should be unconditionally turned on again or the initialization state should be retrieved so that the procedures previously been executed with the network are repeated.
Accordingly, as the error occurs in the CONTEXTs between the network and MS, nothing can be occasionally done by the MS according to the implementation status of the network. Moreover, all the procedures of the channels between the network and MS may be re-executed from the beginning, thereby wasting radio resources as well as introducing other inefficiencies.